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ETHANOL DEVALUATES AN AVERSIVE MEMORY FOLLOWING CONDITIONING IN INFANT RATS R.M Pautassi., S. Sanders, E. Truxell, S. Miller, N. E. Spear & J.C. Molina Instituto Ferreyra, Córdoba, Argentina, Facultad de Psicología, UNC & Dept. of Psychology, Binghamton University, NY. When a neutral cue (conditioned stimulus: CS) is paired with a biologically relevant cue (unconditioned stimulus: US) an associative memory is acquired. Modifications in the US representation after the establishment of a CS-US association are likely to result in changes of the original conditioned response. The aim of this experiment was to evaluate ethanols capability to devaluate an aversive memory acquired during early ontogeny of the rat. Blood alcohol concentrations (BACs) for each of the doses employed in the experiment were also recorded. On postnatal day 14 (PD 14) four conditioning trials were conducted, each one defined by 5 minutes of exposure to a lemon odor (CS) paired with intraoral infusion of citric acid (US). Control pups experienced both stimuli in an explicitly unpaired manner. On PD 15 pups were briefly exposed to the citric acid solution either drug free or five minutes after being intragastrically administered with one of the following EtOH doses: 0.25, 0.5, 1.25 or 2.5 g/kg (devaluation phase). Ten minutes after the administration, BACs attained with these doses were 17, 31, 68 and 104 mg%, respectively. Two hours later animals were tested in a two-way odor preference test (lemon vs. eucalyptus). According to a mixed ANOVA (conditioning x ethanol dose x minute of evaluation), animals administered with 0 or a 2.5 g/kg of ethanol during the devaluation phase exhibited a strong aversion to the lemon scent that lasted throughout the test. The magnitude of the aversion was markedly reduced in animals that received the 0.25, 0.5 and 1.25 g/kg EtOH doses, specially during the last minutes of the evaluation. These results indicate that, very early in the ontogeny of the rat, relatively low doses of ethanol (inducing BACs below 70 mg %) successfully devaluate the hedonic value of an aversive unconditioned stimulus, a capability not shown by higher doses of the drug. The widely known anxiolytic or negative reinforcing properties of the drug might underlie this effect. It is suggested that the unconditioned stimulus devaluation procedure here employed should be considered as a valid experimental alternative in the examination of motivational properties of ethanol. These results indicate that low-dose EtOH abolish the expression of an aversive CR by acting through the representation of the US. This capability is not shared by MDZ, suggesting that EtOHs effects are not Gaba-mediated.

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